This invention relates to improvements in disposable diaper fasteners of the type which use an adhesive bearing strip of tape to retain the diaper on a body such as that of an infant.
One objective of diaper machinery manufacturers is to provide for applying fasteners strips to a diaper web at high speed, using the least amount of material, and using the least complex and most reliable apparatus. Another objective is to provide fasteners that are easy to use and provide a secure attachment from one part of the diaper to another so the diaper will be retained snugly on the body.
Typically, the fastener strips are cut from a roll of paper tape or similar material which has one of its surface coated with a pressure sensitive adhesive. The strip from the roll is fed into the diaper making machine and cut into segments which are transferred by means of a vacuum roll to the moving diaper web. One end of the strip is pressed onto the margin of the diaper and the part of the strip which extends from the margin has a release strip superimposed on it so that said part can be folded over the release strip to thereby conceal the adhesive and prevent the strips from sticking to adjacent diapers after they are packaged. To use the fastener, the folded over part of the strip is peeled off of the release strip to expose the adhesive. The strip is then stretched across the edges of the diaper on the side of the body and pressed on the rear portion of the diaper to retain it on the body.
One of the problems that diaper machinery users have faced is that the available adhesives which are most commonly used to coat the one surface of the strip have poor shelf lives. The adhesive is especially susceptible to loss of its tackiness if it is stored for a considerable period of time in an ambient temperature environment that is above or not much lower than normal room temperature. Usually, special care is taken to prevent the rolls of adhesive coated tape from becoming too warm while they are in inventory.
Most prior art diaper fasteners are structurally complex and require many machine operations to fix them on the diaper web and to place them in a proper condition for packaging the diapers. Structural complexity usually means that a substantial amount of the strip, adhesive and release materials will be used in the fasteners. A fastener design that requires one more square centimeter of adhesive than another, for example, can result in a substantial increased cost factor in the diaper manufacturing business when one considers that a machine will make diapers typically at the rate of 350 or more per minute. In a 24 hour run of the machine, just requiring an additional drop of adhesive on each diaper can increase the amount of adhesive that must be purchased by a substantial amount. Loss of competitive position in the market place and lowering of profit in a diaper manufacturing business can be a consequence of using fasteners that consume any more than an optimal minimum amount of material in the manufacturing process.